Clever hardvare construction, both mechanical end electronic, and a solid comprehension of both 6502 (the ATARI 2600’s CPU) and Z80 (TIMEX) programming are combined to produce the very powerful “Came Changer Interface”. The unit cross-connects your 2600 VCS (Video Computer System) and TS 1000, allowing either one to take control of whole blocks of shared memory. That “shared” memory includes the ROM inside any ATARI game cartridge and “shadow” copies of that ROM in your TS 1000’s RAM. With this system you can download the ROM game to your ZX/TS, disassemble the machine code (6502), make games variations or even create your own game from scratch, and then upload your version back to the 2600 for play.
The system consists of two double-sided, plated-through open boards, professionally constructed. The larger, or mother, board plugs into the back of your unexpanded ZX/TS and connects via ribbon cable to the smaller VCS adaptor board. This latter has male and female edge connectors. One inserts into the cartridge slot in your VCS, while game cartridges can be installed in the other.
The mother-board contains 4 HM6116’s (2K static RAM), and uses some ingenious coding to remap internal RAM above that 8K, for a total of 10k RAM (12k with an extra chip and some soldering). The 4K above RAMTOP contains the actual ROM of the game cartridge. For any size cartridge, the game information is transferred into a long 0 REM statement for storage. Cartridges over 4K are handled using a bank switching technique like ATARI’s. Game execution is accomplished by transferring the game data to the actual bottom of RAM using menu driven software and then placing the TS 1000 in a bus requested mode when power is applied to the 2600.
The smaller cartridge adapter board uses the strength of the fiberglass board to open the VCS and cartridge door slots, and has an on-off switch to allow insertion and removal of cartridges while the system is on.
Menu driven software is supplied on cassette. It includes 2 programs of BASIC and ML which are required to download the cartridges, one for 2-4k games and one for 8K. The 8K game actually works for any size game, but takes longer to SAVE and LOAD, a bother if your actual cartridge is a short one. The third program is called “Change” and that’s exactly what it does. A simple 6502 disassembler and monitor are included in this program. They allow you to review the code and change it at will. This is a very nice feature for those shoot-em-up games where you wish you had “just one more ship”.
The system vorks very well and even comes with high quality RF cables and 3 way switch box for your TV set. You need that switch box, unless you use two sets, to switch back and forth between what your VCS and TS are putting out on channel 3 (or 2). I installed an extra 2K RAM chip as insurance for my disk drives data transfer buffer and found the system 100% compatible with AERCO’s disk drive. With that system combination I can download, save or retrieve any program in seconds. The question of speed though, does lead us to a few negative aspects of the system.
8K cartridges download into what, in effect, are 10K BASIC programs, and we all know how long they take to load from tape. After you modify, or make your new game, you may want ot have an EPROM burned. Also, as the system uses BUSREQ you’ll have trouble using the dynamic RAMs (as in a 16K RAM pack) in other system expansions. Hunter boards, populated with 6116’s, should work, if your decoding is complete.
I had very little trouble loading the program. The menus are simple and the documentation is spartan. That documentation consists of 7 photocopied typewritten sheets. It includes an installation sketch and hand drawn schematic, essential memory map locations and operating instructions. Perhaps the only flaw in an otherwise superb system, the documentation is brief, and has a number of typos, though none are serious.
Huron Valley promises to dress up the paperwork to match the quality of the rest of their system and to produce a “Tuterial” (sic) newsletter for owners. Adapters to allow use of the system on 1500s and 2068s are also in the works. Overall, while less than perfect documentation usually causes a severe downgrade, I must rate the “Game Changer” highly. It is exceptionally powerful and well designed, and could provide the ultimate in inexpensive game play and design system for a total investment of less than $175 (including a TS 1000). Overall rating is a 9 out of 10 and would be higher at a slighly lower price.
One final note about Huron Valley, they are exceptionally helpful and courteous on the phone (the owner’s home phone number is supplied), and must be rated one of the most supportive vendors I’ve met.